This application is the U.S. national-phase application of PCT International Application No. PCT/EP98/07226.
The present invention discloses a hydraulic unit for slip-controlled braking systems having a housing defining a number of bores for accommodating inlet and discharge valves, a pump, a motor for driving the pump, and an accumulator. Such housings also define pressure fluid channels for connecting the valves, pump-receiving bores and accumulator-receiving bores and establishing a hydraulic connection between a brake pressure transducer and several wheel brakes.
Patent application DE 40 13 160 Al already discloses a hydraulic unit for a slip-controlled braking system, wherein several valve-receiving bores for inlet and discharge valves are arranged in a first and second valve row. A pump bore is provided outside the two valve rows in the block-shaped housing, which is oriented transversely to the direction in which the valve-receiving bores open into the housing. Furthermore, a motor-receiving bore oriented vertically in the pump bore is provided outside the two valve rows in the housing. Additional location bores for accumulator elements and damping chambers are located vertically to the axes of the valve-receiving bores, which are separated from the valve rows through the pump bore. There are both inlet and discharge valves in each of the two valve rows, with the discharge valves always being located between the valve-receiving bores of the inlet valves, so that the accumulator elementsxe2x80x94which also act together functionally with the discharge valvesxe2x80x94are arranged in alignment to one pair of discharge valves respectively in the housing. The receiving bores for the accumulator elements are limited on both sides by noise-damping chambers which are hydraulically connected both to the pressure side of the pump and the inlet valves in both valve rows.
Due to the bores for the accumulator elements and the damping chamber, which extend to the side of and at right angles to the axis of the pump-receiving bore, a lot of space is needed to integrate all receiving bores in the housing. Consequently, the ensuing outer dimensions of the block-shaped housing give rise to correspondingly large space requirements for the hydraulic unit in the vehicle. Another disadvantage is that the proposed arrangement of bores in the housing allows no free space for arranging additional receiving bores if the outer dimensions of the block-shaped housing remain the same, so that the hydraulic unit cannot be expanded functionally with the given dimensions. In addition, since the inlet and discharge valves are distributed on both valve rows, pressure fluid attachments which run to the wheel brakes are distributed on both lateral surfaces of the housing and this gives rise to additional space requirements on both sides of the housing as well as for guiding the connecting lines outside the housing.
U.S. Pat. No. 5,449,226 discloses a hydraulic unit for slip-controlled brake systems, whose inlet and discharge valves are provided in valve-receiving bores of two valve rows arranged in an offset position to a pump bore in a housing. Separated by a threaded bore extending perpendicularly into the housing at the level of the pump bore, which is provided for fastening a cover for sealing the inlet and discharge valves, there are several accumulator-receiving bores and noise-damping chambers in a row that are arranged outside the cover and also at equal distances from the side of the pump and threaded bore. The accumulator-receiving bores"" far location away from the side of the pump bore, thus, can be attributed to the cover attachment, cover size and the arrangement of a generously dimensioned silent block (unit holder) which needs space between the accumulator-receiving bores and the cover. The pressure fluid channels are provided only in a vertical and horizontal arrangement in the housing.
Thus, it is an object of the present invention to improve a hydraulic unit of the type described above in such a way that, although the dimensions of the housing are kept as small as possible, all receiving bores can be optimally arranged in the housing and such arrangement can be expanded by simple means to include other functions when the location concepts have a uniform design.
According to the present invention, this object is solved for a hydraulic unit of the type mentioned above by means of a connecting channel which connects the accumulator receiving bore and at least one of the discharge valve receiving bores and a return flow channel connecting the accumulator receiving bore and the pump bore, wherein both the connecting channel and the return flow channel extend at an inclined angle (which either may be the same or different) relative to a plane of the housing parallel to the first end face (or bottom surface in situations when the first end face is disposed at the bottom in operation).